This invention relates to a lattice piece for a large mobile crane and a method of erecting such lattice piece.
Large mobile cranes are transported to the respective sites of operation on public roads. Here, the rules of public road traffic are applicable, in Germany for instance the German Road Traffic Regulations. The maximum admissible weights and also dimensions are specified, for instance. In other countries, similar regulations are applicable.
These regulations lead to the fact that the dimensions of the parts to be transported are limited. As a result, the total size of the mobile crane and therefore also the maximum achievable load capacity and the outreach (load moment) thereof also are limited.
Different approaches for increasing the load capacity have already been formulated. In DE 20 2005 017 362 U1, for instance, it has already been proposed to couple two cranes. From WO 2005/030632 A1 it is known to use two booms on one crane in parallel. In these two proposals, the two booms provided here are connected with each other.
In accordance with another proposal, lateral reinforcements were mounted on both sides of the booms and adjusted by means of a dual derrick (as proposed in DE 100 02 917 A1).
In EP 1 015 374 B1 it is described already to create lattice pieces which are dimensioned slightly smaller than the dimensions of a container, in order to simplify the transport of the lattice pieces. Here, differently profiled corner posts were used. The transport of the lattice pieces was effected analogous to the transport of a container with corresponding connections, as they are known for containers.
Since the booms constructed of the lattice pieces should be slewable on a common axis, all solutions have in common that the width of the assembled booms always was larger than the height. Thus, the known booms have less load capacity in the luffing plane than vertical to the luffing plane. In the case of long and heavy main booms, the maximum length to be erected also is limited by the cross-sectional values of the boom in the luffing plane.
With large radii, the “buckling bar boom” also is greatly loaded by its own weight in the direction of the luffing plane, i.e. high cross-sectional values of the boom provide for high load capacity values.